Recent electronic instrument such as computers, portable terminals, and Personal Digital Assistants (PDAs) generally include an input device for manipulating the electronic instrument by touching the input device with a finger or approaching a finger to the input device. As such an input device, joysticks, touch pads, etc. have been known.
Further, as a sensor, capacitance sensors using capacitance have been known. The capacitance sensors may include a sensor electrode. When a user approaches or touches the sensor electrode, capacitance generated by the sensor electrode is changed. By converting the capacitance change into an electric signal with a capacitance voltage conversion circuit, whether a user touches the sensor electrode or not is determined.
Touch panels may be configured with a plurality of sensor electrodes. Touch panels having an X-Y matrix type include row sensor electrodes that are disposed in each row of the matrix, and column sensor electrodes that are disposed in each column of the matrix. By detecting the capacitance change of each of a plurality of sensor electrodes, coordinates touched by a user are specified.